3 Vertebrates-High

Vertebrates Written by Kira Freed

脊椎动物作者:基拉·弗里德

Introduction Touch your elbow. Feel along the middle of your back. The hard objects you feel inside your body are bones. Bones hold up your body and protect organs such as your brain and heart. Scientists classify animals into two groups. Vertebrates are animals with backbones. Invertebrates are animals without backbones. As you read this book, you will find out what the five groups of vertebrates have in common, as well as what makes each group different.

触摸你的肘部。 沿着你背部的中间感觉。 你在身体里感觉到的坚硬物体是骨头。 骨骼支撑着你的身体，保护着你的大脑和心脏等器官。 科学家把动物分为两类。 脊椎动物是有脊椎的动物。 无脊椎动物是没有脊椎的动物。 当你阅读这本书时，你会发现这五类脊椎动物有什么共同之处，以及每一类动物的不同之处。

A Closer Look at Bones All bones are made of a hard type of body tissue. (Skin and muscles are other types of tissue.) Without bone tissue, your body would just be a big, soft blob. If you've ever seen a bone, you may think it looks dry and lifeless. But the bones inside your body are alive! Some bone cells help to repair broken bones. Others make blood cells. These bone cells are located in bone marrow, a special tissue in the center of some larger bones. Blood travels in and out of living bone tissue, bringing oxygen and other nutrients and taking away waste products. Bones also have nerve tissue, especially in the outer layer, which is why it hurts so much if you break a bone.

所有的骨头都是由一种坚硬的身体组织构成的。 (皮肤和肌肉是其他类型的组织。)没有骨组织，你的身体就只是一个又大又软的一团。 如果你见过骨头，你可能会认为它看起来干燥而没有生命。 但是你身体里的骨头是活的!一些骨细胞有助于修复骨折。 其他的则制造血细胞。这些骨细胞位于骨髓中，骨髓是一些较大骨骼中心的特殊组织。 血液在活的骨组织内外流动，带来氧气和其他营养物质，带走废物。 骨头也有神经组织，尤其是在外层，这就是为什么骨头断了会这么疼。

The skeleton is the strong framework that supports and protects a vertebrate's body. The spine, or backbone, is the special feature of vertebrates. The spine is made up of a series of bones, called vertebrae (VER-teh- bray), which are attached to one another in a way that allows the backbone to bend. At the top of the spine is a hard bony case called the skull. It holds and protects the body's control center— the brain. The human skeleton has 206 bones. Other vertebrates have different numbers of bones. Snakes are vertebrates without arms or legs. Their skeletons are made up of a skull and a very long backbone with ribs attached to it.

骨骼是支撑和保护脊椎动物身体的坚固框架。 脊椎是脊椎动物的特殊特征。 脊柱由一系列的骨头组成，称为椎骨(VER-teh- bray)，它们以一种允许脊柱弯曲的方式相互连接。 在脊柱的顶部是一个坚硬的骨壳，叫做头骨。 它控制并保护身体的控制中心——大脑。 人类骨骼有206块骨头。 其他脊椎动物有不同数量的骨头。 蛇是没有胳膊和腿的脊椎动物。 它们的骨骼由一个头骨和一根很长的脊椎骨组成，脊椎骨上有肋骨。

The ends of many bones are covered with softer tissue called cartilage. Cartilage is rubbery tissue that keeps the hard surfaces of bones from grinding against each other. Other parts of your body have cartilage, too. Feel your nose and ears, which are made of cartilage. Joints are the places where bones meet. Joints allow vertebrates to move in different ways. Some joints, such as your knees, only bend in one direction. Other joints, such as your shoulders, rotate. Still others twist and turn. Cartilage helps all these joints to move smoothly.

许多骨头的末端覆盖着一种叫做软骨的软组织。 软骨是一种橡胶组织，它可以防止骨头坚硬的表面相互摩擦。 你身体的其他部位也有软骨。 摸摸你的鼻子和耳朵，它们是由软骨组成的。 关节是骨头接合的地方。 关节允许脊椎动物以不同的方式移动。 有些关节，比如膝盖，只能向一个方向弯曲。 其他关节，比如肩膀，也会旋转。 还有一些人经历了曲折。 软骨帮助所有的关节活动顺畅。

Different bones of vertebrates serve different purposes. Leg bones are designed to support the weight of an animal while it walks or runs. Most flying vertebrates have hollow, lightweight bones for greater ease of flight. Some smaller bones allow animals to move their feet, hands, flippers, or wings in precise ways to steer their bodies or handle objects such as food.

脊椎动物的不同骨骼有不同的用途。 动物在行走或奔跑时，腿骨是用来支撑其重量的。 大多数会飞的脊椎动物都有中空、轻便的骨骼，以便于飞行。 一些较小的骨头允许动物以精确的方式移动它们的脚、手、鳍或翅膀来控制它们的身体或处理食物等物体。